Supply control for a push-type centrifuge



Jan. 13, 1959 R. SIEGRIST 2,868,381

SUPPLY CONTROL FOR A PUSH-TYPE CENTRIFUGE Filed July 2, 1956 7 A so. 2,7 28% 2Q TI I- 9 To? I I INVENTOR. 700r$5afls7f United States Patent SUPPLY CONTROL FOR A PUSH-TYPE CENTRIFUGE Rudolf Siegrist, Aarberg, Switzerland, assignor to Escher Wyss Aktiengesellschaft, Zurich, Switzerland, a corporation of Switzerland This invention relates to a method for regulating the supply of the material. .to be centrifuged to a push-type centrifuge and afcontrol arrangement for performing the method.

The push-type centrifuge is a continuously operating machine. The material to be centrifuged flows uninterruptedly to the uniformly rotating machine. The liquid is continuously hurled through the strainers. The solid material is continuously passed through the drum and thrust into the receiver.

Such a continuous process requires that the centrifuge be fed uniformly. The material to be centrifuged, which is always a mixture of liquids and solids, is usually led into the centrifuge from a container. To set it to a definite quantity per unit time a throttle element is provided the size of the opening in which can be varied from the outside. If the pressure head in the container, the concentration of the mixture, the structure ofthe solids or the viscosity of the liquids changes, the throttle element must be adjusted accordingly. Variations of the kind indicated always occur. Apart from the fact that the influence on the quantity by the variations which occur in the material can not be readily observed, manual adjustment always permits certain irregularities in the feed for the centrifuge.

The invention aims to provide an automatic feed for the centrifuge, in which the influence of the said variations in the material on the quantity is practically negligible, this being of particular advantage to centrifuges used in the sugar industry. The method according to the invention for operating the centrifuge, is characterized in that the supply of material to the centrifuge is influenced in the sense of constantly maintaining a predetermined value of the power input to the centrifuge.

The method is based on the fact that the power input to the centrifuge forms a basis for measuring the supply quantity of the material because a part of the power is used for accelerating the supplied material to the peripheral velocity of the drum. If for any reason the supply quantity increases then that creates a corresponding increase in the power input to the centrifuge and, by reason of this increase in power input and in accordance with the method of the invention, the supply quantity is reduced, i. e. the change in the supply quantity which caused the increased power input is counteracted.

The drawing shows an example of an arrangement for implementing the method according to the invention. The method will also be described by way of example with reference to this arrangement.

In the centrifuge which is to be supplied with material, a straining drum 2 rotates in a housing 1, the material being distributed over the drum by a rotating funnel 3. An axially reciprocating pusher member 4 serves to convey the material on the drum axially towards the outlet. The drum is driven by an electric driving motor 6 through a belt drive 5. The motor is supplied with electric energy through conductors 7.

The material is led from a container 8 having a stirrer a 2,888,881 Patented Jan. 13, 1959 9 through a pipe 10into the funnel 3 of the centrifuge. The supply is controlled by a throttle element 11 built into the container 8 at'the connection for the pipe 10. It is connected'to a rod 12 pivoted to a lever 14 which can tilt about a pivot 13. A reversible auxiliary motor 15 driving a screw 16 serves to adjust the throttle element. The screw engages a nut 17. on the, free end of the lever 14. The throttle element 11. is opened or closed depending on the sense of rotation of the auxiliary motor 15.

The auxiliary motor 15 is fed from mains 18. -A lead 19 to the motor 15 is taken from one of the conductors ofthese mains. One circuit is closed for each of two positions of a contact arm Nico-operating with contacts 21 and 22; one circuit being the conductor 15 the auxiliary motor 15, a conductor 23 connected there to, the contact 21, the contact arm 20 and a conductor 24 to the second conductor of the mains 18; the other circuit is the conducto'r l9, the auxiliary motor 15, a conductor 25 connected thereto, the contact 22, the contact arm 20 and the conductor 24 to the second conductor of the mains. 18. The circuit 19, 23, 20, 24 drives themotor 15 in a sense to close the throttle element 11 whilst the.circuit\19,2'5, 2l), 24 drives the motor 15 in the reverse sense. i

The arm 20 is connected to a balance beam 26 which is influenced by two electromagnets 27 and 28. The electromagnet 27 islfed from a current transformer 22 by one of the conductors [7fleading to the motor 6 for the centrifuge. It'infiuences one side of the beam 26. The other side is infiuenced .by the magnet 28 the current for which is derived from the mains. 18 Via a rheostat 30.

The arrangement operates as follows: When operating normally, the rheostat 30 is set so that the magnets 27 and 28 balance the beam 26 which is in its mid-position. The arm 20 is thus between the contacts 21 and 22 connected to the conductors 23 and 25. No current is therefore supplied to the motor 15.

If for any reason now, the quantity of material to be centrifuged passing through the throttle element 11 increases, this effects an increase in the power input to the motor 6 of the centrifuge. Thus the current to the mag net 27 increases so that the latter has a stronger in fiuence on the beam 26 than the magnet 28. The beam 26 turns clockwise until the arm 20 strikes the contact 21 and closes the circuit 19, 23, 24. This drives the motor 15 in a sense to. lower the throttle element 11 to restrict its cross-section. This occurs until the decrease of material to the centrifuge has caused the current supply to the motor 6 to return to normal and the magnet 28 can once again balance the effect of magnet 27. The beam 26 and arm 20 thus return to their mid-positions so that current supply to the motor 15 is interrupted and the element 11 is undisturbed.

A decrease in material supplied to the centrifuge reacts oppositely to lower the power input to the motor 6. The current to the electromagnet 27 decreases and the magnet 28 is the more powerful. The beam 26 turns counterclockwise and the arm 20 closes the circuit 19, 25, 24 by striking the contact 22. This causes the motor 15 to rotate in a sense. to open the element 11. This stage opened when the power input decreases and closed when it increases.

Instead of a throttle element, the element responding to changes in power input can co-operate with a different type of arrangement for controlling the "supply of material, for example a slide, a dispensing mechanism, a piston pump, a centrifugal pump or the like.

This arrangement ensures a constant supply even if the structure of the material changes. The quantity per unit time is determined by the setting of the rheostat 30. Since changes in the consistency of the mixture and the quantity of the mixture setup changes in the quantity of solids separated out in the centrifuge, it may be advantageous to accompany adjustment of the quantity controlling throttle element 11 by changes in the number of strokes per minute of the thrust mechanism and, if necessary, changes in the quantity of washing media.

This could be achieved, for example, in that, with a hydraulic drive for the thrust mechanism, the rotary speed of the pump for the control fluid is changed by adjusting the brushes of a commutator driving this pump at the same time as the throttle element is adjusted, and the valves governing the washing media are adjusted simultaneously.

What is claimed is:

1. In combination, a centrifuge of the type including a rotary drive motor, a rotary foraminous drum driven by the motor for separating the solid and liquid components of the material being centrifuged, a pusher member encircled by the drum and shiftable therein in the direction of the drum axis, means forming a rotary drive connection between the pusher member and the drive motor, a flaring distributor member connected with the pusher member and defining therewith a distribution chamber, an inlet to said chamber located on the axis of rotation of the distributor, and an outlet from said chamber adjacent the drum; means for feeding material to be centrifuged to the inlet; a flow control element shiftable in opposite directions from a mid position to increase and decrease the rate of feed of said material; and actuating means responsive to the power drawn by the drive motor for shifting the flow control element in the flow rate increasing direction when the power decreases below a predetermined value and in the flow rate decreasing direction when the power increases above that value.

2. The combination defined in claim 1 in which the means for feeding material to the inlet includes a supply passage connected with the inlet; and in which the flow control element is a throttle valve located in the supply passage.

3. The combination defined in claim 10 in which the drive motor is an electric motor and the actuating means comprises a reversible auxiliary electric motor for shifting the throttle valve; first and second circuits for supplying electrical energy to the auxiliary motor to drive it in flow rate increasing and decreasing directions, respec tively; a source of electrical energy; switch means for selectively connecting the first and second circuits with the source of electrical energy; and means responsive to the electrical input to the drive motor for causing the switch means to connect the first circuit with the source when the input decreases below a predetermined value and to rconnect the second circuit with the source when the input increases above that value.

References Cited in the file of this patent UNITED STATES PATENTS January 13, 1959 Rudolf Siegriat It 1s hereby certlfled that error appears 1n the prlnted speclflcatlon of the above numbered patent requlrlng correctlon and that the send Letters Patent should read as corrected below.

Column 4, line 16, for the claim reference numeral "10" read 2 Signed and sealed this 14th day of April 1959,

(SEAL) Attest:

KARL AXLINE ROBERT C. WATS'ON Attesting Oflicer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2 868, 381 

